The invention relates to a light indicator, comprising an indicator element illuminable by means of a light source. The indicator element is manufactured from a substantially transparent material which is provided with an informative indicator pattern.
It is prior known to outfit e.g. illuminators and indicator panels in exit ways with conventional incandescent lamps or fluorescent tubes. One such example can be found e.g. in Finnish utility model No. 1533. The cited solution comprises a light panel fitted with an illuminator cover, wherein the light of a fluorescent illuminator tube fitted inside the illuminator cover is directed out by way of the perimeter of a panel element mounted in connection with a light source. In this particular solution, the illuminator cover is provided with an elongated, cover-length opening for replacing the fluorescent illuminator tube therethrough from above. However, a drawback with this type of traditional indicator panels is the short service life of incandescent lamps and fluorescent tubes as the exit lights must be switched on all the time.
The Finnish patent No. 98768 discloses an indicator panel, showing permanently the way especially to the exit routes of a building and comprising a plate-like body, light emitting diodes mounted on the body in its back surface and extending therethrough, and light emitting diodes extending through the bottom edge of a frame-like cover set on top of the body. In this cited solution, the light emitting diodes extending through the body are adapted to illustrate the body of an indicator panel, especially over its front surface which is provided with a pattern of an after-luminous material. In addition, the light emitting diodes extending through the bottom edge of the cover are configured as a downward-directed, white-light emitting light source, comprising green and red light emitting diodes, which are arranged successively at the bottom edge of the cover and which illuminate an exit route present below the indicator panel or a direction arrow therefor.
The latter solution is beneficial in the sense that the light source comprises low-power leds, which are capable of providing a sufficiently reliable guidance action at comparatively attractive total costs despite being permanently switched on. However, a pattern of an after-luminous material present on the front surface of an indicator panel, as applied in the cited solution, as well as a string of leds illuminating the same, represent currently outdated technology, which is why, at present, this particular type of illumination objective should be carried out by using solely a downward-directed bank of leds. In the cited solution, however, the lighting action has been exploited unfavourably even in this respect, since the leds delivering light downwards have been mounted on the bottom edge of a cover, from which said leds direct light in a traditional fashion therebelow directly into an air space surrounding the illuminator cover. In this conjunction, however, the light produced by the leds easily dissipates in the ambience, e.g. as a result of the leds being soiled or e.g. in smoky conditions, and hence the cited solution is not capable of making it sufficiently certain that a direction arrow or the like present below this type of indicator panel would indeed be illuminated in an emergency.
It is an object of a light indicator of this invention to provide a decisive improvement over the above problems and, thus, to substantially raise the available state of the art. In order to accomplish this object, a light indicator of the invention is principally characterized in that the indicator element is designed as a waveguide panel, wherein light beams propagate with total reflection and get outcoupled therefrom with a diffractive outcoupling system, such as a grating structure or the like, which is configured as an indicator pattern, for producing an indicator pattern activable in the indicator element by the action of light, such that divergent recesses and/or grooves of various sizes and/or shapes constitute divergent local gratings of various sizes and/or shapes, such as multi-shaped and/or binary pixels and/or units, the filling factor, shape, profile and/or size thereof being optimized in such a way that the diffraction efficiency is a function of place.
Diffractive structures refer in optics to all fine structures of a surface, which condition the passage of light on the basis of the diffraction effect. Thus, the details of fine structures must be in the same order of magnitude as the wavelength of light, even smaller than that. Most prior known microprismatic structures are not even diffractive structures as conditioning the passage of a beam therein is based on the refraction effect. On the other hand, the hologram is not a grating, whereas the grating does not produce a three-dimensional image or light. The local grating, in turn, refers to a local grating unit, such as e.g. a pixel. Furthermore, the entire grating structure may be constituted by a great variety of miscellaneous grating units.
The most important benefits gained by a light indicator of the invention include its simplicity, efficiency, and reliability in operation, since, in this conjunction, it is first of all possible to make use of very low-power leds as a light source. On the other hand, by virtue of a total-reflection based waveguide panel construction utilized in the invention, the light source can be optimized in all aspects since it is possible to minimize unintentional reflection losses and other light losses. On the other hand, the invention also makes it possible for a light indicator to function in a so-called active fashion, i.e. in such a way that, first of all, when the light source is disconnected from the entire indicator element or, for example, from a given section of the indicator pattern, this section is by no means visible, since, according to the basic concept of the invention, a desired indicator pattern is only activated to be visible as a result of light guided therein. Thus, it is possible to use one and the same indicator element for arrows pointing in different directions in such a way that the direction arrow needed at a given time is activated as required by the situation, the arrow pointing in the opposite direction being invisible.
By virtue of a principle exploited in the invention, it is further possible to make extremely thin structures, which can be embedded in a substrate, or else to manufacture flexible or preformed structures by providing every time such conditions that the limit or threshold angle of total reflection is not exceeded in the panel element. The invention makes it further possible to design the panel element for example as a box-type structure, such as a quadratic or tubular xe2x80x9clamp postxe2x80x9d, inside which the light reflects with total reflection and emerges only at the outcoupling system so as to activate nothing else but a given desired indicator pattern or the like. Furthermore, another possible application for a light indicator of the invention is that one and the same indicator pattern carries for example portions activable at various wavelengths for providing various indicator images, said application being of course implementable also by modifying the intensity/operating voltage of a light source, etc.